Load selector for tapped transformers with insulating cylinders unrolling within each other



Nov. 8, 1955 2,723,318

B. JANSEN' LOAD SELECTOR FOR TAPPED TRANSFORMERS WITH INSULATINGCYLINDERS UNROLLING WITHIN EACH OTHER Filed March 7 1951 IN VENTOR5512mm JANSEN 43:. AT'roRNEYs,

LOAD SELECTOR FOR TAPPED TRANSFORMERS WITH INSULATING CYLINDERSUNROLLING WITHIN EACH OTHER Bernhard Jansen, Regensburg, GermanyApplication March 7, 1951, Serial No. 214,282

8 Claims. (Cl. 200--6) This invention relates to load tap selectors fortapped transformers and particularly for transformers having hollowinsulating cylinders with parallel axes and rollable one within theother.

In tapped transformers of small and medium output load tap selectors, i.e. tap selectors switching under load, usually the stationary loadswitching contacts connected to the transformer tappings are fixed on astationary outer insulating hollow cylinder, and the counteracting loadswitching contacts are movably mounted on an inner hollow insulatingcylinder rollable on the inner surface of the outer cylinder. Such loadtap selectors may be built single-phase or polyphase, the p'olyphase tapselectors being built only for application onthe neutral point of thetransformer. In order to guide the movement of the inner rollablecylinder, the polyphase tap selectors have been built only forapplication on the neutral point of the transformer and this has beenaccomplished by providing an elongated metal axle extending throughoutthe length of the inner rollable cylinder and by means of eccentricdrives on the upper and lower ends of said cylinder. Such an elongatedmetal axle is objectionable as it causes a disturbing influence,especially if in the polyphase load tap selector each phase is assignedits own load changeover switch part having phase potential, since thestationary and movable contacts must be completely insulated from thecontacts of the neighboring phase. An elongated insulating axle is alsoobjectionable as it would take up too much space unless the diameter ofthe load tap selector were increased to uneconomical dimensions.

It is therefore an object of the present invention to provide means forguiding and controlling the movement of the innerrollable cylinderwithout the necessity of using an elongated axle either of metal or ofinsulating material.

It is another object of the invention to maintain the axes of the outerand inner cylinders in parallelism without the necessity of using anelongated axle either of metal or of insulating material.

It is another object of the invention to insulate the load tap selectorparts of the individual phases completely from each other, without thenecessity of increasing the dimension of the cross-section of the loadtap selector.

It is another object of the invention to provide a load tap selectorwherein the body of the inner rollable cylinder is used to transmit thetorque necessary for its rolling movement from one end of the body tothe other.

It is another object to provide improved means for urging the gear teethof the inner rollable cylinder'into continuous meshwith the gear teethof the outer fixed cylinder.

Other objects and advantages of the invention will be apparent from thedescription thereof to follow taken in connection with the accompanyingdrawings in which Fig.1 is a vertical sectional view of a load tapselector for a three-phase transformer embodying my invention,

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the view being taken on the plane of the line I-I of Fig. 2.

Fig. 2 is a horizontal sectional view taken on the plane of the line IIof Fig. l. I

Fig. 3 is a horizontal sectional view taken on the plane of the lineIIII of Fig. 1.

Fig. 4 is a horizontal sectioinal view taken on the plane of the lineIHIII of Fig. 1.

With particular reference to the drawing, Fig. 1 shows a three-part loadswitch for a polyphase current transformer which is to efiect theregulation at the three-phase ends of the transformer whichconduct theentire operat ing voltage. This is, in general, necesary both for powertransformers connected in delta and for booster transformers operatingin open series connection. The load selector head is fastened to thetransformer cover by screws passing through packing material between thehead and cover. The selector head supports the load switch oil containerconsisting of an outer hollow insulating cylinder Za having a bottom endclosure plate to which is connected the container for the contaminatedoil.

Supported on the cylinder Za adjacent its upper end is a group or seriesof spaced stationary contacts U1, U2, U3, U4 arranged in a circle asshown in Fig. 3. A similar group or series of stationary contacts V1,V2, V3, V4 is supported below and spaced and insulated from the U-groupof contacts; and a similar group or series of stationary contacts W1,W2, W3, W4 is supported below and spaced and insulated from the V-group'of contacts. These contacts are connected to the transformer taps of thethree-phase current windings. These groups of contacts are at all timesin normal operation. One of the contacts U1, U2, U3, U4 is connected bythe shunt contact Au to the conductor or bus bar Sr: of the cylinder Za.One of the contacts V1, V2, V3, V4 is connected by the shunt contact Avto the conductor or bus bar Sv. One of the contacts W1, W2, W3, W4, isconnected by the shunt contact Aw to the conductor or bus bar Sw. Theseconnections are effected in any manner well known in the art.

Referring to Fig. l, the load switches corresponding to the three-phasesU, V, W are designated Lu, Lv, Lw,

respectively. Such a load switch forms no part of the present invention,but one form of such switch is shownl in Fig. 3 wherein a main contact His shown in contact with the tap U2 of the transformer so that currentis taken therefrom and fed through the shunt contact Au to the currentshunt Su. The auxiliary switch contacts ha and hb are connected in thecustomary manner to the main contact H by switch-over resistances, andserve for the load switching during uninterrupted operation.

In the same manner, the current of the transformer phase V is'taken fromtap V2 and conducted through shunt contact Av to the current shunt Sv.Similarly, the current of the transformer phase W is taken from tap W2and conducted through shunt Aw to the end of the load switch from whereit passes over the current shunt Sw.

The current shunts or conductors Su, Sv and Sw can be switched by theload selector to the other taps U1 to U4, V1 to V4 and W1 to W4.

In order to effect the switching of the main contact H (Fig. 3), forinstance, from tap U2 to tap U3, the main contacts H of the threetransformer phases, together with the auxiliary contacts ha and hb,together with the switchover resistances (not shown in the drawings),are supported and insulated from each other on an inner hollowinsulating cylinder Zi, the axis m of which is arranged uninterruptedoperation. The inner cylinder Zi is mounted to roll in the outerinsulating cylinder Za by means of the structural parts. describedhereinafter. Such parts are arranged in the load selector head and inthe opposite end of the selector in such a manner that the main contactsH (Fig. 3) first of all rises in the path of a cycloidal curve, in thewell known manner, from contact U2 and then swings around in an arc tocontact U3, upon which it seats, in a radial direction. For thispurpose, the central axis In of the inner cylinder Zi is offset adistance equal to the space indicated by the arr w r (Fig. l) to bringit into parallelism with and eccentric to the axis M of the outercylinder Za. This is effected by means positioned in the load selectorhead including a crank cam E and by means positioned in the opposite endof the load selector including pins Z1 and Z2 which engage each other asshown in Fig. 1.

Inasmuch as in each contact group Lu, Lv, Lw which correspond to thethree phases U, V, W, respectively, considerable contact forces areproduced, due to the spring action of the load switch contacts and theshunt contacts coming into contact with each other, there is a tendencyon the part of the inner insulating eylinde. Zz' to move out laterallyto avoid these spring forces. This movement is prevented in the presentinvention by the rigid connection between the cylinders provided by themeshing of the teeth R1 formed on the outer periphery of the top endplate of the inner cylinder Zi with teeth R2 of a ring mounted on theinner surface of the outer cylinder Za at its upper end, and by themeshing of the teeth R3 formed on the outer periphery of the closureplate on the bottom end of inner cylinder Zi with the teeth R4 of a ringmounted on the inner surface of the outer cylinder Za at its lower end.These teeth however can only prevent such lateral movement when and ifthey are in mesh or in engagement with each other. Such meshing is onlycertain when the inner cylinder Z1 is in proper position relative to theouter cylinder Zn, that is, when the axis m of the inner cylinder Z! isoffset from the central axis M of the outer cylinder Za a distance equalto the distance r for the entire length of said inner cylinder. Toaccomplish this in the present invention, a pin Z1 is mounted on anddepends from the plate closing the lower end of the inner cylinderdirectly in line with its axis In. A similar pin Z2 is mounted on andextends upwardly from the plate closing the adjacent lower end of theouter cylinder Za. Pin Z2 is directly in line with the axis M of theouter cylinder. The upper pin Z1 rests on and contacts the lower pin Z2,the lower pin thus serving as a bearing for the upper pin. In order toavoid frictional wear of the two pins, one of them is preferably rigidlyfastened to its cylinder while the other is rotatably mounted ondouble-cone hearings or the like on its cylinder. In order to facilitatethe insertion of the inner insulating cylinder, the pins are preferablyformed with slight tapers running in opposite directions. Fig. 1 showssuch pins Z1 and 22 only at the lower or load selector end. At the upperhead end of the selector, the crank cam E is rotatably mounted with itsupper pin journalled in the head and arranged in line with the centralaxis M of the outer insulating cylinder Zn, and with its lower pinjournalled in the top closure plate of the inner cylinder Zi in linewith the axis In of the inner cylinder. The crank cam E thus serves tomaintain the gear teeth of the cylinders in mesh. In order to preventmotion of the eccentric crank cam E in either a clockwise orcounterclockwise direction, under the pressure forces of the three maincontacts H and the shunt contacts Au and Av and Aw, the crank cam E islocked in its various operating positions by spring-pressed pawls K1 andK2 which are pivctally mounted in the selector head with the gearportion R1 of the upper closure plate of the inner cylinder Zi.

'Iihe forcenecessary for the cycloid-like switching movement of the maincontact H from the transformer tap U2 to tap U3, for example, isprovided as follows: housed in the load selector head is a coiled ortorsion spring device or accumulator indicated generally at F. Aprotruding portion of this spring acts upon a part of the crank cam E.The spring is wound to the extent of the angle necessary for theswitching operation by a bevel gear operatively connected thereto andwhich is operatively connected to a source of power. When the windingoperation is finished, the pawl lock is released in any well knownmanner to permit movement of the cam. If the pawl K2, for example, isdisengaged, the spring acting upon the crank cam E is free to turn thecam in the direction of the arrow in Fig. 2. In this way, the crank camE can rotate in a clockwise direction under the action of the springdevice F from the radial position corresponding to U2 to the radialposition corresponding to U3 and is therefore moved a distance equal to5 of the total circumference. The crank cam E simultaneously rolls theupper part of the inner cylinder Zi with its upper gear teeth R1 rollingeccentrically in the spaces between the teeth R2 of the outer cylinderZa, which rolling movement is transmitted to the cylinder Zi, the axisin thereof rotating around the main axis M of the outer cylinder. Therolling motion of the inner cylinder Zi stops when the crank cam E isagain caught by the two pawls K1 and K2 and held fast in the radialdirection looking toward tap contact U3. This movement from the radialposition U2 to the radial position U3 results because the gears R1 andR3 on the upper and lower closure plates, respectively, of the innercylinder Zi, each has only eleven teeth for rolling in the spacesprovided by the twelve teeth on each of the gears R2 and R4,respectively, on the outer cylinder Za. Due to the difference in totallengths between the spaces provided by the eleven teeth and the spacesprovided by the twelve teeth, there results, upon an 5 rotation of thecrank cam E, a difference in distance of movement of a size of onetooth. This corresponds to the distance of the step or movement from U2to U3. During this movement, the connections between main contact H andU2, ha and U2, hb and U3, and H and U3 become disengaged. As the maincontact H is directly connected to the shunt contact Au and to theauxiliary contacts ha and hb in any well known manner, such as by ohmicresistances, no interruption of the circuit takes place by the aforesaidmutual disengagements of the contacts. A load switching under load istherefore effected by insertion of switchover resistances.

It is important that the inner insulating cylinder Zi remains, in allphases of its motion, in axial parallelism with the central axis of theouter insulating cylinder Za so that the corresponding stationary andmovable contacts will always properly contact or engage each other. Thisaxial parallelism is assured in accordance with the present invention bythe relative arrangements of the inner and outer teeth in the loadselector head and in the opposite load selector end as well as by thefixture of the eccentricity of the axes M and m, which are offset fromeach other a distance equal to the radius r, by means of the cam E andthe lower tapered pins Z1 and Z2.

I claim:

1. A load tap selector for tapped transformers including an outer hollowinsulating cylinder, an inner hollow insulating cylinder rollable on theinner surface of said outer cylinder, said cylinders being positionedwith their axes in parallelism, means for rolling said inner cylinder,stationary contacts mounted on the inner surface of said outer cylinder,movable contacts carried by said inner cylinder and mounted on the outersurface thereof, said rolling means for said inner cylinder including atop end plate of the inner cylinder, teethformed upon the outerperiphery of said plate, aring mounted onthe inner surface of the outercylinder at the upper end thereof, teeth formed on said ring, saidrespective teeth intermeshing, and also including a closure plate on thebottom end of the inner cylinder, teeth formed on the outer periphery ofsaid closure plate and a toothed ring mounted on the lower end of theinner surface of the outer cylinder, said last two sets of teethrespectively intermeshing.

2. A load tap selector for tapped transformers including an outer hollowinsulating cylinder, an inner hollow insulating cylinder rollable on theinner surface of said outer cylinder, said cylinders being positionedwith their axes in parallelism, means for rolling said inner cylinder,stationary contacts mounted on the inner surface of said outer cylinder,movable contacts carried by said inner cylinder and mounted on the outersurface thereof, and means for maintaining the parallelism of the axesof said cylinders, the means for rolling said inner cylinder including aspring-pressed device operatively connected to one end of said innercylinder, said rolling means for said inner cylinder including a top endplate of the inner cylinder, teeth formed upon the outer periphery ofsaid plate, a ring mounted on the inner surface of the outer cylinder atthe upper end thereof, teeth formed on said ring, said respective teethintermeshing, and also including a closure plate on the bottom end ofthe inner cylinder, teeth formed on the outer periphery of said closureplate and a toothed ring mounted on the lower end of the inner surfaceof the outer cylinder, said last two sets of teeth respectivelyintermeshing.

3. A tap selector switch of the class described, comprising: a hollowouter cylinder; a plurality of relatively stationary contact meanselectrically insulated from each other, said stationary contact meansbeing carried by said outer cylinder and disposed in spaced relationshipabout the internal peripheral portion thereof; an inner cylinderdisposed within said outer cylinder and having its longitudinal axisparallel to and spaced from the longitudinal axis of said outercylinder; movable contact means carried by said inner cylinder andselectively engageable with said stationary contact means; internallytoothed ring gear means fixed to said outer cylinder; externally toothedgear means fixed to said inner cylinder and meshing with said ring gearmeans; means for producing rolling motion of said externally toothedgear means relative to said ring gear means; and interengaging axiallyextending means comprising one portion carried by said outer cylinderand another portion carried by said inner cylinder, said axiallyextending means maintaining said longitudinal axes in fixed spacedparallel relationship during said rolling motion.

4. A switch according to claim 3, in which said axially projecting meanscomprises a pin of circular crosssection carried by said outer cylinderand a pin of circular cross-section carried by said inner cylinder, theexternal circular surfaces of said pins interengaging each other duringsaid rolling motion.

5. A switch according to claim 4, in which said pins are axially taperedin opposite directions.

6. A tap selector switch of the class described, comprising: a hollowouter cylinder; a plurality of relatively stationary contact meanselectrically insulated from each other, said stationary contact meansbeing carried by said outer cylinder and disposed in spaced relationshipabout the internal peripheral portion thereof; an inner cylinderdisposed within said outer cylinder and having its longitudinal axisparallel to and spaced from the longitudinal axis of said outercylinder; movable contact means carried by said inner cylinder andselectively engageable with said stationary contact means; internallytoothed ring gear means fixed to said outer cylinder; externally toothedgear means fixed to said inner cylinder and meshing with said ring gearmeans; and crank means comprising one portion pivotally and axiallyconnected to said outer cylinder and another portion pivotally andaxially connected to said inner cylinder, rotary movement of said crankmeans causing rolling motion of said externally toothed gear meansrelative to said ring gear means, said crank means maintaining saidlongitudinal axes in fixed spaced parallel relationship during saidrolling motion.

7. A switch according to claim 6, in which said stationary contact meansare uniformly spaced and wherein said two gear means are provided withteeth arranged to cause displacement of said movable contact means fromone stationary contact means to an adjacent stationary contact means inresponse to rotation of said crank means through one completerevolution. I 8. A switch according to claim 7, further comprisingcontrollable spring actuated means connected to said crank means, saidspring actuated means driving said crank means through one completerevolution upon each actuation thereof.

References Cited in the file of this patent UNITED STATES PATENTS2,231,627 Jansen Feb. 11, 1941 FOREIGN PATENTS 705,659 Germany May 6,1941 886,836 France July 19, 1943

